The invention relates to pneumatic tires which have a smooth tread pattern except for the presence of aquachannels.
It is generally recognized in the tire art that tires suitable for use on aircraft must be capable of operating under conditions of very high speeds and large loads as compared to tires used on automobiles, busses, trucks or similar earthbound vehicles. As used herein and in the claims, a tire is xe2x80x9csuitable for use on an aircraftxe2x80x9d if the tire is of a size and load range, or ply rating, specified in either the YEARBOOK OF THE TIRE AND RIM ASSOCIATION, or the YEARBOOK OF THE EUROPEAN TIRE AND RIM TECHNICAL ORGANIZATION, for the year in which the tire is manufactured, or in the current U.S.A. military specification xe2x80x9cMIL-PRF-5041xe2x80x9d.
In the prior art, nylon is a preferred reinforcement material for aircraft tires because it is forgiving and is not as subject to fatigue as other available materials. Nylon reinforcement, however, does not have superior strength, and for heavy aircraft, many plies of nylon are needed in the construction of an aircraft tire.
It is also known that in view of its high modulus (80,000 MPa) and dimensional stability, aramid is particularly advantageous as a reinforcing element in high-speed tires. As is used herein, xe2x80x9caramidxe2x80x9d is understood to mean a manufactured fiber in which the fiber-forming substance is generally recognized as a long, chain synthetic aromatic polyamide in which at least 85% of the amide linkages are attached directly to two aromatic rings. Representative of an aramid or aromatic polyamide is a poly p-phenyleneterephtalamide.
Aircraft tires are sometimes made with smooth tread, i.e., the tread has no grooves or sipes. Usually, aircraft tires are made with circumferential grooves, i.e., the tread is smooth except for the presence of the circumferential grooves. In a common aircraft design, the tread has four (4) circumferential grooves which provide a void area in the footprint of about 15 percent. The circumferential grooves help prevent hydroplaning when an aircraft using such tires lands and takes off, and to some extent, helps prevent sideways skidding of the aircraft.
It is a continuing goal in the art to improve the wear properties, skid properties and other performance properties of aircraft tires.
A pneumatic tire of the invention comprises at least one pair of annular beads, at least one carcass ply wrapped around the beads, tread disposed over the at least one carcass ply in a crown area of the tire, and sidewalls disposed between the tread and the beads. The tread has a depth of 0.20 to 0.50 inch. Two aquachannels, each having a width comprising 4.5% to 7% of the tread width, and a depth comprising 63% to 83% of the tread depth are disposed in the tread. The width of the central portion of the tread, between the aquachannels, comprises 90% to 110% of the total width of the two shoulder tread portions.
An illustrated embodiment of the fire is made with four nylon carcass plies and two aramid breakers.
Specific fire sizes that have been constructed for initial testing are sizes 5.00-5, 6.00-6, 15xc3x976.0-6, 6.50-8, 6.50-10, 22xc3x976.75-10, 7.00-6, and 8.50-10.
The tire of the invention has load specifications and inflation specifications for use on an aircraft.
Definitions
xe2x80x9cBeadxe2x80x9d means that part of the tire comprising an annular tensile member wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim.
xe2x80x9cCarcassxe2x80x9d means the tire structure apart from the belt structure, tread, undertread, and sidewall rubber over the plies, but including the beads.
xe2x80x9cCrownxe2x80x9d refers to the circumferentially outermost portion of the carcass substantially within the width limits of the tread.
xe2x80x9cEquatorial plane (EP)xe2x80x9d means the plane perpendicular to the tire""s axis of rotation and passing through the center of its tread.
xe2x80x9cFootprintxe2x80x9d means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under design load and pressure.
xe2x80x9cFootprint Net-to-grossxe2x80x9d refers to the actual footprint of a deflected tire and is the ratio of the ground-contacting surface area of the tread to the total tread footprint area including the groove void area.
xe2x80x9cGroovexe2x80x9d means an elongated void area in a tread that may extend circumferentially or laterally about the tread in a straight, curved, or zig-zag manner. Grooves ordinarily remain open in the tire footprint.
xe2x80x9cSipesxe2x80x9d refer to small slots molded into ribs of tire that subdivides the tread surface and improves traction characteristics. Sipes tend to close completely in a fire footprint.
xe2x80x9cNormal load and inflation pressurexe2x80x9d refers to the specific design inflation pressure and load assigned by the appropriate standards organization for the design rim and service condition for a tire of specific size. Examples of standards are the Tire and Rim Association Manual and the European Tire and Rim Technical Organization. 
xe2x80x9cPneumatic tirexe2x80x9d means a laminated mechanical device of generally toroidal shape (usually an open-torus) having beads and a tread and made of rubber, chemicals, fabric and steel or other materials. When mounted on the wheel of a motor vehicle, the tire, through its tread, provides traction and contains the fluid that sustains the vehicle load.
xe2x80x9cRadialxe2x80x9d and xe2x80x9cradiallyxe2x80x9d are used to mean directions radially toward or away from the axis of rotation of the tire.
xe2x80x9cShoulderxe2x80x9d refers to the upper portion of sidewall just below the tread edge.
xe2x80x9cSidewallxe2x80x9d means that portion of a tire between the tread and the bead.
xe2x80x9cTreadxe2x80x9d means a molded rubber component which, when bonded to a tire casing, includes that portion of the tire that comes into contact with the road when the tire is normally inflated and under normal load.
xe2x80x9cTread widthxe2x80x9d means the arc length of the road contacting tread surface in the axial direction, that is, in a plane parallel to the axis of rotation of the tire.
xe2x80x9cTurn-up plyxe2x80x9d refers to an end of a carcass ply that wraps around one bead only.